ACC deaminase-producing rhizosphere competent spp. mitigate salt stress and promote growth by modulating ethylene metabolism.

Plant growth-promoting rhizobacteria (PGPR) are known for growth promotion and mitigating environmental stresses. Here, we examined the propitiousness of three indigenous salt-tolerant PGPR, i.e., (NBRI 28B), (NBRI 33 N), and (NBRI 12 M) for plant growth promotion and salt stress amelioration in . Results of the in vitro plant growth-promoting attribute revealed NBRI 12 M demonstrated the highest values at 1 M salt (NaCl) concentration. Furthermore, the greenhouse experiment using three strains confirmed plant growth-promoting and salt stress-ameliorating ability, through colonizing successfully and mitigating the adverse effects of ethylene by modulating 1-aminocyclopropane-1-carboxylic acid (ACC) accumulation, ACC-oxidase (ACO), and ACC-synthase (ACS) activities under salt stress. sp. inoculation has also induced plant response for defense enzymes, chlorophyll, proline and soluble sugar under salt stress. Among three strains, NBRI 12 M not only demonstrated higher values for plant growth-promoting (PGP) attributes but also the same was observed in the greenhouse experiment. Thus, the outcomes of this comparative study represent for the first time that salt-tolerant strains exhibiting multiple PGP attributes under salt stress along with high rhizosphere competence can alleviate salt stress by reducing the stress ethylene level in the host plant.